Update .travis.yml

removed support for 5.3 and added 7.2

Author: Raaghu

.travis.yml

@@ -1,15 +1,15 @@
 language: php
 
 php:
-  - '5.3'
   - '5.4'
   - '5.6'
   - '7.0'
   - '7.1'
+  - '7.2'
   - 'nightly'
 
 before_script:
   - composer update
 
 script:
-  - ./vendor/bin/phpunit -c phpunit.xml 
+  - ./vendor/bin/phpunit -c phpunit.xml